Distribution and geological control of mud volcanoes and other fluid/free gas seepage features in the Mediterranean Sea and nearby Gulf of Cadiz

Abstract

Existing knowledge on the distribution of mud volcanoes (MVs) and other significant fluid/free gasventing features (mud cones, mud pies, mud-brine pools, mud carbonate cones, gas chimneys and, in some cases, pockmark fields) discovered on the seafloor of the Mediterranean Sea and in the nearby Gulf of Cadiz has been compiled using regional geophysical information (including multibeam coverage of most deepwater areas). The resulting dataset comprises both features proven from geological sampling, or in situ observations, and many previously unrecognized MVs inferred from geophysical evidence. The synthesis reveals that MVs clearly have non-random distributions that correspond to two main geodynamic settings: (1) the vast majority occur along the various tectonosedimentary accretionary wedges of the Africa-Eurasia subduction zone, particularly in the central and eastern Mediterranean basins (external Calabrian Arc, Mediterranean Ridge, Florence Rise) but also along its westernmost boundary in the Gulf of Cadiz; (2) other MVs characterize thick depocentres along parts of the Mesozoic passive continental margins that border Africa from eastern Tunisia to the Levantine coasts, particularly off Egypt and, locally, within some areas of the western Mediterranean back-arc basins. Meaningfully accounting for MV distribution necessitates evidence of overpressured fluids and mud-rich layers. In addition, cross-correlations between MVs and other GIS-based data, such as maps of the Messinian evaporite basins and/or active (or recently active) tectonic trends, stress the importance of assessing geological control in terms of the presence, or not, of thick seals and potential conduits. It is contended that new MV discoveries may be expected in the study region, particularly along the southern Ionian Sea continental margins.

Deep-seated hydrocarbons in the seep “Brecciated Limestones” of the Maiella area (Adriatic foreland basin): Evaporitic sealing and oil re-mobilization effects linked to the drawdown of the Messinian Salinity Crisis

“…The Messinian evaporites are generally considered to act as an efficient seal to ascending basinal fluids (e.g., Loncke et al, 2004;Pawlewicz, 2004;Bertoni and Cartwirght, 2005). Most of the present-day mud volcano provinces in the Mediterranean Sea occur where Messinian evaporites are thin or absent, suggesting that thick evaporite covers can be regarded as a cap-rock preventing deep fluid leakages to the seabed (Mascle et al, 2014).…”

Mud Volcanism in a Canyon: Morphodynamic Evolution of the Active Venere Mud Volcano and Its Interplay With Squillace Canyon, Central Mediterranean

“…Calabria Crotone Basin C a l a b r i a n E s c a r p m e n t Mascle et al, 2014). Calabria Crotone Basin C a l a b r i a n E s c a r p m e n t Mascle et al, 2014).…”

Intra- to post-Messinian deep-water gas piping in the Levant Basin, SE Mediterranean

“…The Messinian evaporite unit exerts major control on basin fluid flow across the Mediterranean (Lastras et al, 2004;Cartwright, 2005, 2014;Gradmann et al, 2005;Zitter et al, 2005;Netzeband et al, 2006b;Camerlenghi and Pini, 2009;Clari et al, 2009;Hübscher et al, 2009;Micallef et al, 2011;Iadanza et al, 2013;Natalicchio et al, 2013;Mascle et al, 2014). Although the Messinian evaporite serves as regional seal (Bertoni and Cartwright, 2005;Gardosh and Tannenbaum, 2014), there are compelling evidences documented over the last decade suggesting fluids bypassing this supposedly sealing sequence albeit most of which have been documented along the Northern and Southern Levant margin (Bertoni and Cartwright, 2005;Frey-Martinez et al, 2005b;Fuhrmann, 2010;Netzeband et al, 2006b;Reiche et al, 2014).…”